Certain known cable transportation systems include systems in which the transportation units are suspended from a pull cable, such as chair-lifts or cable-cars, as well as urban transportation systems of the type described in EP Patent Number 0 687 607 B1 and EP Patent Number 1 088 729 B1, in which the transportation units rest on rails and are drawn by a pull cable.
In both of these known cable transportation systems, the auxiliary drive device comprises a succession of wheels aligned along the passenger station. The wheels are rotated by a mechanism operated by the pull cable or, in alternative embodiments, by an actuator independent of the cable, and engage the transportation unit to move it along a given path portion in accordance with a given optimum speed profile comprising a deceleration stage and an acceleration stage.
The wheels of the auxiliary drive device are connected to one another by a drive belt looped about two pulleys. Each wheel is integral with a respective pulley and, by appropriately selecting the pulley diameters, the speed of the adjacent wheel can be increased or reduced to accelerate or decelerate the transportation unit.
Since the auxiliary drive device may comprise curved portions—as in the case of auxiliary drive devices at turnaround stations of cable transportation systems such as chair lifts or cable-cars—power is transmitted between adjacent wheels of the auxiliary drive device using bevel gears; each wheel is integral with a bevel gear meshing with a bevel gear interposed between the two adjacent wheels.
Though effective, currently used auxiliary drive devices are extremely complicated to produce, on account of the high degree of precision involved in assembling the belt, pulley, and bevel gear connections. Moreover, currently used auxiliary drive devices are not very flexible, and fail to provide for easy, relatively low-cost variations in speed.